Synthesis of carbon nanotubes by microwave plasma enhanced CVD on silicon using iron as catalyst

Microwave plasma enhanced chemical vapor deposition (MPECVD) technique has been successfully used to synthesize vertically aligned carbon nanotubes with uniform diameter on a silicon wafer using iron as catalyst. A template has been used to pattern the catalyst film and grow nanotubes on the patterned blocks. Critical process parameters, such as source gas concentration, pretreatment time of catalyst film and growth time are varied and their effect on nanotube growth is studied. Pulsed laser deposition technique is used to deposit thin film of the catalyst film (1--5 nm) on the substrate surface. Improvement in alignment is observed with increase in methane flow rate. The optimum flow rate of methane is found to be between 20 and 30 sccm. Entire catalyst coated area has deposition with increase in pretreatment time. Growth time of 5 min with methane flow rate of 15 sccm and a pretreatment time of 5 min is found to be optimum for obtaining vertically aligned CNTs. Multi-walled nanotubes with diameters in the range 20--125 nm are synthesized in the present investigation.